At present, there has been no existing rescue equipment that can be used to accommodate a large group of people and provide oxygen for over 72 hours in underground mines in China. When an accident occurs in an underground mine, a large amount of the toxic gas is usually generated. The composition of the gas which has toxic effects on humans basically falls into 3 types:
1. Compositions causing asphyxiation or coma;
2. Compositions causing irritation to sensory organs or respiratory system;
3. Other toxic compositions.
From the death toll statistic information of mine accidents, most of the victims died of inhalation of toxic gas such as carbon monoxide. Due to the block-up or submergence of the mining tunnels, the miners could not flee through the mining passageways and the possibility of their survival is minimal. This is one of the major reasons that there have been so many deaths in mining accidents in China.